This discussion was very helpful.
I was able to get the footage in my situation from a 7 11 and at first they said no.
Then I explained all the things that could be done and reminded them it is a publicly accessible lot.

It ony takes any lawyer a few minutes to issue a subpoena and require the footage to be turned over as part of an existing court case, if one exists.
Easy and quick to do, but don't wait in those situations as the footage could be erased or discarded at some point.

You can simply ask for the footage, and if the holder of the footage will not provide it, then a subpoena can be ordered and you will obtain everything available. It's not really that complicated an issue.